Change notebook's stylesheet?

I want to create an Stylesheet based on Stylesheet Outine. This Stylesheet can be found in: Menu Format → Stylesheet → Utility → Outline. However, when I click on a blank line, a text cell (Title, Section, etc. ) appears and not an Input cell. Is there a way to change this procedure?

Regards.
Sinval

From the Format menu select Style / Input (Cmd - 9 on a Mac).

This procedure I am familiar with and should apply whenever I want to insert a math input cell. I would like to know if there is a way to permanently change how it works in Stylesheet defaut.

In that case, you should edit your question to make it clear that you want to know how to change the default style.

This can be done in several ways, check this workflow doc for details.

Rohit I am grateful for the information.